Natural variation of ClCCT promoter promotes flowering and dwarfing in adlay (Coix lacryma-jobi L.)

The flowering time is a key trait that determines adaptation, yield and quality of crops. Adlay, a traditional cereal crop, has developed a distinctive agricultural industry in Southwest China and Southeast Asian countries. However, the currently planted varieties are all semi-domesticated landraces with delayed flowering and excessive height. These defects limit yield improvement per unit area and mechanized harvesting. In this study, a major QTL associated with flowering time and plant height in adlay has been mapped and identified as ClCCT , a gene having a conserved function and regulatory pathway for inhibiting flowering time and increasing plant height in gramineous crops. Among the six identified haplotypes of ClCCT, the haplotype with 38-bp insertion in promoter region of ClCCT has earlier flowering time and wider geographical distribution than other haplotypes. The insertion variation, which arises from the segmental duplication of ClCCT , can inhibit the expression level of reporter gene and has been used in breeding for early maturity and dwarfing. These research results not only reinforce our understanding of the importance of CCT domain protein in the tropical crops adapting to high-latitude environment, but also provide a validated breeding target for the early maturity and dwarfing of adlay.